The easiest place to drain it is into the washing machine standpipe, if that location is accessible. The drain is under pressure so it can be piped to a higher elevation than the water softener.

: I am planning to install a water softener in the crawl space of my house, but I'm not sure of the best way to run the drain line. Would it be better to run the drain line directly to the exterior of the house, such as to a french drain or can the drain line be installed in the existing drain lines in the house? If the drain can be installed in the drain lines, how would the standpipe be installed since this area is lower than the rest of the house? Thanks in advance.